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2025 PEA Q9

Out of 20 questions, average correct =11.7= 11.7, average wrong =5.3= 5.3. Has the TA made a mistake?

Reveal answer and solution

Answer

A

Solution

  1. 1

    For every student, correct ++ wrong =20= 20. Taking averages,

  2. 2
    correct‾+wrong‾=20. \overline{\text{correct}} + \overline{\text{wrong}} = 20.
  3. 3

    But 11.7+5.3=17≠2011.7 + 5.3 = 17 \ne 20.

Answer structure / marking notes

A linear identity preserves under averaging --- the sum of averages must equal 2020.

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Content note

Imported from public/resources/isi/msqe/solutions/pea/2025/ISI_MSQE_PEA_2025_Solutions.tex. Question wording is retained from the available local TeX source; incomplete option blocks or ambiguous source status are flagged for review.